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os: Make sure big requests have sufficient length.

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A client can send a big request where the 32B "length" field has value
0. When the big request header is removed and the length corrected,
the value will underflow to 0xFFFFFFFF.  Functions processing the
request later will think that the client sent much more data and may
touch memory beyond the receive buffer.

Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
This commit is contained in:
Michal Srb 2017-07-07 17:04:03 +02:00 committed by Eric Anholt
parent c2f2b25ab5
commit 9c23685009
1 changed files with 5 additions and 0 deletions
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5
os/io.c
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@ -441,6 +441,11 @@ ReadRequestFromClient(ClientPtr client)
if (!gotnow)
AvailableInput = oc;
if (move_header) {
if (client->req_len < bytes_to_int32(sizeof(xBigReq) - sizeof(xReq))) {
YieldControlDeath();
return -1;
}
request = (xReq *) oci->bufptr;
oci->bufptr += (sizeof(xBigReq) - sizeof(xReq));
*(xReq *) oci->bufptr = *request;